Automotive heat exchanger assemblies commonly have a core comprising tubes, separators or fins, and side plates made of some type of metal, such as aluminum, and associated headers. These heat exchangers also comprise end tanks or manifolds made of plastic or metal. The purpose of the header is to attach the end tank or manifold firmly to the core portion of the heat exchanger. To provide for efficient heat exchange and to avoid potentially overheating due to loss of thermal liquid or gas within the heat exchanger, the tank to header joints must be essentially leak-proof. Typically the tank to header joints are made ‘leak tight’ by providing for a seal, such as a rubber gasket, between the header and the tank.
The problem with current designs is that the gasket, and, in particular, the rubber gasket often used between the header and the tank, is often misaligned or otherwise improperly positioned, either due to improper assembly procedures or faulty design of seal or gasket. Such a misalignment is often not detectable at the first stages of assembly or testing, due to the fact that the location of the seal is not visible on external examination. Detection of the misalignment is made more difficult since the seal, though incorrect or incomplete, may make the tank to header joint appear to be leak proof and the heat exchanger may appear to be functioning properly, due to the fact that the misalignment or otherwise improper positioning of the gasket lead to it somehow being ‘wedged’ or ‘pinched’ in place during assembly, leading to the formation of a temporary seal. Since this temporary seal may be capable of lasting through traditional leak testing procedures performed after initial assembly at the manufacturing facility, the fact that it is defective vis-à-vis its use in the normal heat exchanger operating environment, may not be apparent until the heat exchanger is shipped to a customer assembly plant for further processing, or even during vehicle use by the end customer, which can lead to disastrous consequences.
One approach to solving this problem is illustrated in U.S. Pat. No. 5,899,267, which adds ribs which project from the interior wall of the end tank in order to hold in a gasket that is incorrectly positioned so that it can form a seal, while nevertheless, allowing the defective or not properly assembled joint gasket to exist and to hold back or contain fluid. The ribs may also prevent an inappropriately positioned gasket from being displaced during initial leak testing, to prevent the catastrophic loss of fluid. In addition, inappropriately positioned and/or pinched gaskets can have resultant tears and/or induced gasket surface defects or flaws, that reduce the life of the seal, and, thus, the effective lifetime of the heat exchanger assembly. The solution of U.S. Pat. No. 5,899,267 may, therefore, lead to the unexpected effect of shipping parts, with improperly positioned gaskets and/or other defects or flaws, to the customer or end consumer.
The heat exchanger assemblies of the present invention, with means to detect temporary seals at the tank to header joint, as described below, have not been described in this prior art.
Heat exchangers also often have connections or fittings areas where a fluid connection exists between assemblies. The problem with most prior art fittings is that the fittings may not be leak-tight or leak proof in that fluid (gasses or liquids) in the system that pass through the fitting are able to leak or escape in an undesirable fashion. The fittings most common in the prior art consist of a male or portion to be inserted into a female or receiving portion for the inserted or male portion. An example of prior art fittings can be found in numerous sources, including standard SAE specifications.
SAE J1926-1 and J1926-2, for example, illustrate a fluid connection fitting with the female and male portions or end portions of a fluid connection (See FIGS. 1 & 2). The male fitting portion (male portion of the fitting) has grooves or threads (2) that match up, interrelate or interlock with grooves or threads on a female fitting portion (female portion of the fitting) to retain and/or maintain the two portions in interlocking or interrelated contact. The fluid connection fitting further has a rubber compound O-ring that is located between or against the male and female fitting portions such that it forms a seal so that fluid (liquid or gas) cannot escape from the joint (6) formed at the male and female fitting portions. The male and female fitting portions are both metal or metallic alloy components that are manufactured to fit tightly or snugly when placed in their proper positions, with the O-ring insuring the ‘complete’ seal.
U.S. Pat. No. 4,372,374A, EP571263A1, and U.S. Pat. No. 6,192,583 disclose attempts to direct and control the path of fluids that are capable of leaking at connections or fitting areas. These applications are drawn to heat exchangers, and, in particular, heat exchangers that contain more than one fluid, and attempt to keep fluids, when different, from inappropriately mixing if one or more portions of the heat exchanger itself should experience a fluid leak. In particular, a ‘leak path’ is created that can direct or control the fluid to prevent such inappropriate mixing of fluids.
Another example of the use of a leak path is found in JP10197188A. A supplemental ‘hole’ is located on the heat exchanger so that if the heat exchanger's individual component parts are not correctly assembled, and, therefore, an inappropriate leak of fluid somewhere occurs, some fluid will be detected at the area of the hole, and, subsequently, the heat exchanger will not pass standard leak test set up to ensure that no inappropriate leaks occur prior to sending out for its final use. Use of such a leak path in this disclosure is particularly pertinent to joints, and, specifically, brazed joints.
As described above, in a typical prior art threaded fitting with a rubber O-ring seal connection, the metal or metallic alloy portions of the male and female fitting portions are built to fit snugly when in their proper position, with the rubber O-ring providing the ‘complete’ or leak tight or proof seal. The connection fitting is designed so that the leak tight or proof seal is verified by standard leak test methods prior to being sent out for its final use or validated as meeting specification requirements. The test would then confirm that the complete seal has been achieved and that the heat exchanger could now be shipped to the end customer.